Mechanisms of SHP-1 P2 promoter regulation in hematopoietic cells and its silencing in HTLV-1-transformed T cells.
The Src homology-2-containing protein-tyrosine phosphatase 1 (SHP-1), is a negative regulator of cell signaling. It is also considered a tumor suppressor gene because of its ability to antagonize the action of tyrosine kinases. Although SHP-1 is expressed strongly in hematopoietic cells, decreased expression has been observed in various hematological malignancies, which suggests a central involvement of SHP-1 in leukemogenesis. We have shown previously that human T cell lymphotropic virus type-1 (HTLV-1) Tax-induced promoter silencing (TIPS) is an early event causing down-regulation of SHP-1 expression, which is dependent on NF-kappaB. In this study, DNase I footprinting and EMSA also revealed binding of transcription factors, specificity protein 1 (Sp1) and octamer-binding transcription factor 1 (Oct-1) to the P2 promoter, and site-directed mutagenesis confirmed that these factors contribute to the basal P2 promoter activity. Chromatin immunoprecipitation (CHIP) assays showed that Sp1, Oct-1, NF-kappaB, CREB-1, and RNA polymerase II interacted with the core SHP-1 P2 promoter in CD4+ T cells and Jurkat cells but not in HTLV-1-transformed MT-2 and HUT102 cells when HTLV-1 Tax is present. Furthermore, bisulfite sequencing of the SHP-1 P2 core region revealed heavy CpG methylation in HTLV-1-transformed cells compared with freshly isolated CD4+ T cells and HTLV-1-noninfected T cell lines. A significant inverse correlation between degree of CpG methylation and expression of SHP-1 mRNA or protein was observed. Taken together, our data support the notion that in HTLV-1-transformed CD4+ T cells, TIPS causes dissociation of transcription factors from the core SHP-1 P2 promoter, which in turn leads to subsequent DNA methylation, an important early step for leukemogenesis.
Nakase
Koichi
K
Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney St., Boston, MA 02115, USA.
Cheng
Jihua
J
Zhu
Quan
Q
Marasco
Wayne A
WA
D001483:Base Sequence; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D018899:CpG Islands; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D019175:DNA Methylation; D005786:Gene Expression Regulation; D020868:Gene Silencing / Q000502:physiology*; D006410:Hematopoiesis / Q000502:physiology*; D015368:Human T-lymphotropic virus 1 / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism; D050811:Octamer Transcription Factor-1 / Q000378:metabolism; D011401:Promoter Regions, Genetic; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6 / Q000235:genetics / Q000502:physiology*; D012319:RNA Polymerase II / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism* / Q000821:virology
C115163:CREB1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; D016328:NF-kappa B; D050811:Octamer Transcription Factor-1; D016329:Sp1 Transcription Factor; D012319:RNA Polymerase II; C509249:PTPN6 protein, human; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6